Electrostatographic copying apparatus

ABSTRACT

An electrostatographic copying apparatus comprising a combined illumination and fixing unit, a novel original feed employing a flexible transparent transport sheet, a perforated suction drum preferably having a sponge material surface to strip copy sheets from the imaging drum, a developer material applicator comprising a chamber having movable walls to bring the developer into contact with the drum, and a drum cleaner comprising a web in contact with the drum.

United States Patent 1191 Mi halik ELECTROSTATOGRAPHIC COPYING APPARATUS [76] Inventor: Nandor Mihalik, Geranium,

. I Molesey Rd., Walton-on-Thames, England 221 Filed: Mar.3l,l97l 21 Appl. N6; 129,668

[30] Foreign Application Priority Data Apr. 1, 1970 Great Britain 15349/70 1451 May 7, 1974 3,649,115 3/1972 Hodges .l 355/11 3,186,838 6/1965 Graff et a1. 355/15 x 3,427,106 2/1969 516a 355/11 x FOREIGN PATENTS OR APPLICATIONS 11.313 6/1967 Japan 355/15 207,934 7/1966 U.S.S.R.' 1. 355/10 112,554 3/1966 Netherlands 355/3 1,120,900 7/1968 Great Britain 355/3 309.784 4/1969 Sweden.... 355/3 Primary ExaminerFred L. Braun Attorney, Agent, 0r Firm-Fleit, Gipple & Jacobson [5 7] ABSTRACT An electrostatographic copying apparatus comprising a combined illumination and fixing unit, a novel original feed employing a flexible transparent transport sheet, a perforated suction drum preferably having a [56] References Cited sponge mater1al surface to strip copy sheets from the UNITED STATES PATENTS imaging drum, a developer material applicator com- 3,397,630 8/1968 Pratt 355/106 prising a chamber having movable walls to bring the 3,628,440 l2/l97l Czarnikow.... 95/89 R developer into ontact the drum and a drum 21959-095 l W960 Magnum)" 355/ cleaner comprising a web in contact with the drum. 3,637,303 l/l972 Komori et al 355/8 3.597.074 8/1971 Murgas et a1. 3-55/8 UX 16 Claims, 6 Drawing Figures iATENTEDMAY 1 sum 1 or 2 Nandor Mih-alip By 7 92%zwflmz Attorney;

ELECTROSTATOGRAPHIC COPYING APPARATUS This invention relates to improvements in electrostatographic copying apparatus.

Electrostatographic copying apparatuses are well known to comprise, essentially, an exposure station whereat an original is illuminated, optical means to direct an image of the original onto a drum having a previously charged surface of photoconductive material, so that this material is discharged in areas corresponding to light parts of the original, a developer unit which directs developer material, often mixed with a carrier, against the drum, so that the developer material is electrostatically retained at the charged areas of the drum, a transfer station whereat the so developed image is transferred to a sheet of copy material, and a fixing station wherein the developer is fixed or fused onto the copy sheet.

The improvements of the invention may be used to- 'gether or singly in electrostatographic copying apparatus, and are generally relatively simple and therefore easy to produce.

According to the present invention there is provided electrostatographic copying apparatus including an exposure station and a light source for the exposure of originals to be copied, and a fixing unit for fixing developer material onto a copy sheet by the application of heat, wherein the light source is in or adjacent the fixing unit and heat from the light source is used in the fixing unit.

Preferably the light source is located within thermoinsulating walls which define the fixing unit, the walls having a transparent section through which light may pass.

In one form the fixing unit has an opaque flap movable to and from a position in which it covers the transparent section. In another form there is associated with the light source a rotatable shield which directs radiation from the light source through the transparent section or towards a copy sheet according to its rotational position. The fixing unit may have additional heat sources.

The invention also provides electrostatographic copying apparatus wherein an original to be copied is moved past an exposure station at which it is illumi nated, such apparatus including a substantially horizontal exposure window at the exposure station and a flexible transparent sheet windable onto and off a roll and adapted, while being wound onto the roll, to be drawn over said window, such that an original to be copied when placed upon the sheet is moved over the window.

A drive roller may be provided to contact the roll of transparent sheet to wind it up. The roll of transparent sheet is suitably located at the free end of a flap which is hinged to the housing of the apparatus. The flap can be retained in an operative position wherein it-is substantially coplanar with the window.

The invention further provides electrostatographic copying apparatus including an imaging drum on which an electrostatic image may be formed and developed by the application of developer material, and a transfer zone in which the developed image is transferred to a copy sheetin contact with the imaging drum, and including stripping means for removing copy sheets from the imaging drum comprising a movable perforated member located adjacent the imaging drum to contact the copy sheet and to retain the copy sheet by suction.

The movable member is preferably a drum, and preferably has a foam material surface which can contact the imaging drum without damaging it.

Further, according to the invention, there is provided electrostatographic copying apparatus having a rotatable drum on which an electrostatic image may be formed and developed by the application of developer material, and a transfer station whereat the developed image may be transferred to a copy sheet, and including cleaning means comprising a first spool on which a roll of cleaning material may be mounted to be resiliently urged against the drum, and a second spool onto which the cleaning material may be wound from the roll.

An alternative cleaning means may be provided, thus the invention also provides electrostatographic copying apparatus including a rotatable drum on which an electrostatic image may be formed and developed by the application of developer material, and a transfer zone whereat the developed image may be transferred to a copy sheet, and including cleaning means comprising a first spool for a roll of cleaning material in web form and a takeup spool for said cleaning material, and two rollers adapted to urge cleaning material passing from one spool to the other against the drum and a suction tube terminating between the said two rollers.

There is also provided, according to the invention, electrostatographic copying apparatus having a drum on which an electrostatic image may be formed and a developer unit for developing said electrostatic image by the application to the drum. of a developer material, said developer unit including a chamber for developer material located beneath the drum and having at least one movable wall, which is movable so that the level of developer in the chamber is raised or lowered, such that the developer may be brought into or out of contact with thedrum, and means to move the wall.

The features of the invention are not only simple and easy to produce, but are generally of a space saving nature compared with known equivalent features of electrophotographic copying machines.

In order that the invention may be more clearly un' derstood, the following description is given, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic side view of an improved copying apparatus according to the invention;

FIG. 2 is a similar view to FIG. 1 of part of the apparatus of FIG. 1 when in its operative position;

FIG. 3 is an enlarged view of the developer unit shown in FIG. 1;

FIG. 4 is a view, similar to FIG. 3, of an alternative form of developer unit which may be incorporated in the apparatus of FIG. 1;

FIG. 5 shows an alternative drum-cleaning unit which may be included in the apparatus of FIG. 1; and

FIG. 6 shows a modified version of a heater and lighting unit which may be included in the apparatus shown in FIG. 1.

The apparatus shown in FIG. 1 comprises a drum 10 provided in known manner with a photoconductive surface layer (for example of vitreous selenium or selenium-sulphur), the drum being rotatable (clockwise as shown in the drawing) by means of a main drive of the apparatus transmitted (by means not shown) from a main drive motor 11. In operation, this drum functions in known manner. Each part of its sensitive surface is uniformly charged electrostatically as it passes a corona device 12, which may consist of a wire at high voltage stretched in a partly open shell of plastic material, after which the charged drum surface passes through an exposure zone 13 at which there is projected on to it, by means of an optical system to be described, an image of a document or other original which is being copied. Exposure of the drum surface leaves it bearing an electrostatic latent image corresponding to the optical image projected on to it, and on continued rotation of the drum this latent image is developed by means 'of a developer unit 14 also to be described in greater detail. At a transfer zone 15 the deance of a further corona or similar device 16, to sheet material which, at a stripping zone 17, is then stripped from the drum to be fed through a fixing unit 18 which renders the transferred developed image permanent on the said sheet material which is then ejected from the apparatus by exit rollers 19 of which one is driven by the main drive.

In the illustrated apparatus, the optical image projected on to the drum at the exposure zone 13 is formed by an optical system which cornprises an exposure window 20, a lens unit 21 and mirrors 22 and 23.'This optical system projects on to the drum 10 a focussed image of an object (such as part of a document) which is in contact with the upper surface of the window 20.

To maintain zero (or substantially zero) relative movement between'a given part of an image and a particular point on the drum surface as both move together through the exposure zone 13, it is necessary to move the object across the window (from right to left in F IG. 1) and to rotate the drum 10 at appropriate speeds.

To effect this movement in the case of a thin original document, such as a sheet or a small number of sheets of paper stacked together, the apparatus shown in FIG. 1 is provided with original feed means in the form of a saddle 24 mounted over the window 20. The window 20 is itself mounted with its upper face flush with a flat upper external surface 25 of the machine. The saddle 24 incorporates two rollers 26 and 27 each of which coveloped image is transferred, preferably with the assistoperates with a respective roller journalled in the machine proper or with a respective low-friction stationary member, such as an inset strip of polytetrafluoroethylene, of which the upper surface provides a nip with the roller 26 M27 respectively. In this illustrated case the rollers 26 and 27 would each be driven by the main drive so that an original document slid manually leftwards along the upper surface would be positively engaged in the nip between the roller 26 and the member or alternative roller therebelow and fed thereby at the appropriate speed over the viewing window, and into the nip between the roller 27 and lower member or alternative roller therebeneath. Preferably a guide plate 30 is provided above the window in the saddle 24 to ensure that the document follows the desired path. It will be understood that while the original document is being thus passed over the viewing window 20 at predetermined speed its image is being projected to the exposure zone 13 as a moving image which moves in register with the part of the surface of the rotating drum 10 which is moving through the exposure zone.

In the saddle 24, the rollers 26 and,27, and the guide plate 30, are preferably capable of slight upward movement against the bias of springs (not shown) so that some variation in thickness of the original document being fed can be accommodated. In an alternative arrangement the saddle contains only a guide plate and springs which urge it downwardly into light contact with driven rollers mounted in the body of the machine on either side of the exposure window. The guide plate is either made from or surfaced with a layer of lowfriction material such as polyethylene.

The saddle 24 is preferably removably secured to the main body of the machine. In the illustrated embodiment, a drive arrangement such that the drive train to the rollers engages automatically when the saddle 24 is fitted in position is preferably provided. Thus, the rollers 26 and 27 may be linked by a chain drive, with one of the rollers having a gear wheel which meshes with another gear wheel on the main body of the machine, preferably with some vertical play. Projection of the optical image at the exposure zone 13 is by illumination of an original at the exposure window 20. This illumination may be provided, as has been customary in document copying machines, by means of a light source provided specifically for the purpose. In known machines, however, such light sources often produce not only light but also a great deal of heat which is not utilised and often constitutes a problem; and it is preferred in apparatus according to the present invention to use as the source of light a radiant element which is also utilised as a source of heat in the fixing unit 18. Thus, in the apparatus illustrated in FIG. 1, the fixing or fusing unit 18 comprises a floor 54 and a chamber defined thereabove by upwardly converging walls of thermally insulating material. Within the unit 18 is at least one radiant element 55 which provides both heat (for fixing the powder image on the sheet of material advanced over the floor 54) and light for illuminating the original document as this is passed over the exposure window 20. To allow light to pass, part of a thermally insulating wall is a hingedly mounted flap 56 which is opened'to the positions indicated in broken line, when illumination is required. Loss of heat by convection is prevented by the provision of a transparent cover 57 of suitable heat-resistant transparent material such as heat-resisting glass. To make the illumination as even as possible, a light reflecting surface 58is preferably provided where it will reflect a portion of the light which the exposure window '20 reflects rather than transmits. The surface 58 is preferably arranged so that it is not visible to the mirror 22; and all parts of the inside of the apparatus which are visible to the mirror 22 (except the window 20) are preferably blackened. Preferably, also, baffles are included which prevent light from reaching the lens 21 except by reflection at the mirror 22, and preferably, the element 55 is so positioned that the reflection of its image from the expo sure window 20 does not pass to the lens 21. The heat generated by the element 55 may well be sufficient for the unit 18, but one or more additional heater elements 59 may be provided if desired. Depending on the temperature and distance of the heater element or elements from the sheet material on which the image is to be fixed, it may be desirable to shield the sheet material by means of one or more metal plates or other noninflammable shields 59' between the elements and the sheet material. Preferably the space around and above the unit 18 is ventilated by a constant stream of air through it, for example the air which may be sucked from the interior of a perforated drum 51, if this is a suction drum for the purposes of stripping copy sheets from the imaging drum 10, or from a separate fan. Preferably, also, the floor 54 is normally raised at least at its right-hand end as shown to close the entry slit and thereby minimise heat loss therethrough except when the slit is required to be open because sheet material is being fed therethrough. The floor 54 may also be so mounted that it can be lowered to give access to the interior of the unit 18 for manual removal of any sheet material which may, as must occasionally be expected, become jammed therein. I

In the combined illuminating and heating unit 18 shown in FIG. 1, only a part of the light emitted is available for illuminating the window 20. This proportion may be increased by an arrangement such that as the flap 56 hinges open a reflector element not shown) rotates to a position below and partiallysurrounding the element 55, thereby to reflect up to the window 20 light emitted in other directions by the element 55. If this arrangement is employed, it is of course preferable so to arrange theapparatus that heat is not required below the element 55 at the times when illumination is required above it. In a modified embodiment shown in FIG. 6, the movable reflector actually replaces the hinged flap and thus serves a double function. As shown in FIG. 6, the upper part of the thermally insulating walls of a unit 18 is constituted by a curved wall of heat resisting glass 57'; and between this and the radiant element 55 is disposed a generally hemicylindrical reflector 90 which normally reflects both light and heat downwardly. When illumination of the window 20 is required, however, the reflector 90 is rotated to a position 90' shown in broken lines below the elenient-SS. As with the unit shown in FIG. 1, the space above and around the unit shown in FIG. 6 is preferably cooled by a stream of air. 7

The advantages of the combined heating and illumination unit include compactness and simplicity of construction, and a saving of power, as fewer and smaller heating elements are required. Furthermore, in known machines it has been necessary to provide a fan or the like to dissipate the heat generated by the light source, and this waste of energy is avoided in the inventive constructions. In countries where. grid voltage is comparatively low these savings are especially advantageous.

As noted above, the saddle 24 is preferably removable, the reason being to enable the apparatus to copy pages from bound books and other relatively thick originals. To this end the apparatus comprises, as shown in FIG. 1, an extension 65 which isnormally folded down but which can be secured in a raised position as indicated in broken lines in which it provides an extension of the flat upper surface 25. The extension houses a take-up roller 66 on which is normally wound a flexible clear'plastic sheet 67, for example a polyester film such as Melinex. The outer, free end of the sheet 67 has secured to it a transverse bar or handle 68 by which, as better seen in full line in FIG. 2, the sheet 67 can be pulled off the roller 66 until the bar 68 is at the righthand end of the surface 25. An original to be copied, such as a face-down opened book 69 FIG. 2) can then be placed on the extended sheet 67 and drawn over the viewing window 20 at the appropriate speed by winding in the sheet 67 at that speed. To provide this constant- I speed wind-up, a roller 70, which is spring-urged into contact with the roller 66 or the sheet already wound thereon, is conn ectable to the main drive (at least when the extension 65 is in its raised condition) by means not shown which, preferably, starts the wind-up of the sheet 67 andthe feed of the copy sheet material from roll 44 simultaneously or in other predetermined time relationship. Alternatively,-the roller may ensure that the sheet 67 winds up properly on the spool 66, while the actual speed of take-up is controlled by a drive roller 70' rotating at the appropriate speed. By the time the handle 68 reaches the window 20, as shown in broken lines in FIG. 2, a complete copying scan of the book 69 has been made, and further copies may be made in similar manner by drawing back the handle 68 to its maximum extent and repeating the process.

In its folded-down position shown in FIG. 1, the extension 65 must not obstruct the delivery of copies from the rollers 19 and so it preferably includes a slidable panel 71 which, when the extension 65 is folded down, leaves an opening 72 adjacent the exit rollers 19 but which, in the raised position of the extension 65 slides to close this opening and provide uninterrupted support for the sheet 67 and whatever original it is carrymg.

In order to protect the sheet 67'against scratching, which would impair its transparency, the upper surface 25, and that of the extension 65, are preferably finished with some soft low-friction material, for example, a sheet of woven silk.

The surface of the drum 10, after passing under the corona device 12 and through the exposure zone ,13, bears an electrostatic latent image which requires to be developed. Conventionally, development is usually achievedby cascading downwardly over the drum surface, where this is steeply inclined a mixture of fine toner powder and coarser carrier particles. This mixture cascades from a higher level to a lower level, and is then returned to the higher level by lifting means such as a belt-and-bucket conveyor, or a. rotary conveyor constituted by a rotating disc provided with peripherally disposed buckets, or a rapidly turning rotor which actually throws the mixture up again to return it to the higher level/All these known developer devices must be of considerable size in relation to the drum size, since they include regions both above and'below the not inconsiderable) part of the drum surface over which the developer mixture cascades, as well as space to accommodate the lifting means; and indeed the size of, particularly, a small document copying machine has in the past been conditioned in no small measure by the minimum practical size of the developer unit it was to incorporate. By contrast, the developer unit 14 is of a different and novel kind which can be of relatively small size and which does not employ cascade development.

The developer unit shown in FIG. 1 is illustrated on a larger scale in FIG. 3, while FIG. 4 illustrates a slightly different form of developer which operates on the same principle.

As clearly shown in FIG. 3, the developer unit disposed below the drum 10 has developer mixture 35 contained between two hingedly mounted plates 40. When these are in their lowermost position as shown in full line, the developer mixture 35 is all below the level of the drum 10, but when the plates 40 are pivotally raised to positions 40 shown in broken lines the level of the developer mixture is raised to 41 and it makes bulk contact with the drum 10. As shown in FIG. 4, a developer unit disposed below the drum 10'has developer mixture 35 supported on a flexible sheet 42 suspended at its edges. Below the sheet 42 are .two bars 43 which are displaceable towards one another to positions 43 in whichthey cause the sheet 42 to assume a raised position 42 in which it holds the'developer mixture 35 up in bulk contact with the drum. Rotation of the drum causes agitation of the mixture in the chamber. The bars 43 may be mounted with their ends in respective horizontal slots in end-plates of the developer unit, to be moved towards one another (by means not shown) only when an image is to be developed. Similarly the plates 40 in FIG. 3 may be operated only when development of an image is required. Alternatively, in both embodiments the movable parts may be repeatedly moved to form a cloud of toner, which will be attracted to the imaging drum in its charged areas. In both embodiments, the movements may be caused by cams or like mechanical devices rotated by the main drive motor, with followers on or associated with the moving parts. I

As toner powder is attracted into adherence with charged parts of the drum surface to form a developed image thereon, new toner powder must be'added to the developer mixture, and the developer unit 14 is provided with a toner-powder replenisher device, for instance a hopper which discharges material when the level of toner in the developer unit drops below a certain level.

The side plates of the developer units shown extend to near the imaging drum to reduce the unwanted flow of developer out of the unit.

Besides its relatively small size and simple construction and its generally more convenient position directly below the drum, the described developer units 14 have certain other advantages which may besaid to stem from the fact that it does not provide cascade development. The bulk contact" of the developer mixture with the drum, by which they operate, requires only relatively small and slow movements of the developer mixture, and thus the generation of free-floating dust (toner powder) is minimised. This obviates the need for tight seals between the developer unit and the drum surface and this, together with the convenient shape of the developer unit, makes for easy removal of the unit from the apparatus when desired. The absence of cascading and consequently of rapid carrier. particle movement means that there is very little tendency for spillage or leakage to occur, even though no tightseal to the drum is provided. Further, the lack of any violent impact means that there is little or no tendency for any caking of the toner powder to occur. It will be noted also-that there is no shutter such as is often provided to control cascading in known developer units, and this also helps in simplification.

As already noted, the above-described developer units are relatively convenient to remove, as small selfcontained units, from their operative positions; and advantage may be taken of this to make different coloured prints at will, simply by removing a developer unit containing toner powder of a non-desired colour and replacing that unit by another containing toner of the desired colour. By an extension of this facility, fullcolour prints may be made. The apparatus would require suitable filters to be provided in the optical system, so as to expose the drum successively to different coloured component images by successive use of differ ent filters during successive passes of the original, a single copy paper have transferred-to it, in register, a series of developed images developed on the drum by means of different developer units containing toner of different colours. This multiple cycle process could, in fact, be performed automatically by the machine if it were provided with the necessary plurality of developer units and means for selecting each in turn, as well-as the necessary control circuitry and means for re-cycling the single copy sheet in proper register (as well as repeated scanning of the original). Space for the necessary circuitry and other ancillary components such as fans will, however, be available within the apparatus for example the space 91in FIG. 1.

As the part of the surface of the drum which bears a developed image emerges from the developer unit 14, it is necessary to feed to it a sheet of material such as paper to which the image may be transferred. In the apparatus shown in FIG. 1 this sheet material is drawn from a roll 44 by rollers 45 and 46, of whichone is driven at the appropriate time by the main drive (or which may be rotated continuously but is brought into pinching and driving engagement with the sheet material only at the appropriate time); and the sheet 'materialis advanced past a guillotine device 47 and between guides 48 (one of which may be constituted in part by the outer surface of the developer unit 14 although it is not so shown) to a second paper feed means constituted, in the illustrated apparatus, by a driven roller 49 in pinching engagement with a stationary member 50 with a surface of low-'frction material such as polytetrafluorethylene. Once the material being fed from the roller 44 is taken up by the roller 49, a sheet of the desired length can be cut off by appropriately timed actuation of the guillotine 47, leaving an end of the material still between the rollers 45 and 46 ready to be advanced thereby as the leading end of a subsequent sheet when this is required. The rollers 45 and 46 may be arranged to run slightly faster than the roller 49, so that a slight slackness builds up near the guillotine 47 and allows the guillotine action to take place while this slack is being taken up by the roller 49.

The sheet advanced by the roller 49 is brought into non-slip contact with the surface of the drum 10 to which it adheres electrostatically, and advances therewith under the corona device 16 which assists in transferring the toner/powder, constituting the developed image, from the drum surface to the contacting surface of the material. The sheet material and the image transferred to it are then stripped from the drum 10 at the stripping zone 17 by any convenient means such as a rotating perforated suction drum 51, from the interior of which air is sucked and which accordingly strips the sheet material from the drum 10 and holds it round a peripheral part of the suction drum. A plate 52 is lo-- cated on the inside of the drum 51 and covers about three quarters of its circumference. Thus the suction effect is only available between the stripping zone 17 and the heating unit 18.

The perforated surface of the drum is preferably formed with spaced annular grooves (not shown) into which stationary fingers 53 can extend so as to separate 7 the sheet material from the perforated surface where the suction effect is removed as the sheet passes over the upper edge of the cover plate 52. By this means, the leading edge of the sheet of material is led on to and over the floor 54 of the fixing unit 18.

The suction roller may be in the form of a sponge roller or a roller having an opened pored foamed material surface mounted on a central perforated shaft from which the air is sucked; in this case, the roller can actually contact the drum, in the absence of a copy paper, without damage to the surface; and the same is true of a variant in which a sponge roller attracts by virtue not of suction but of an electrostatic charge applied to it for the purpose.

Both these arrangements have the advantage that the widthof copy paper being used is immaterial to the stripping apparatus. Thus, there is no need to adjust the separation of grippers, or to arrange the stripping means carefully so that it does not contact or damage the imaging drum. Also, because considerable force may be required to overcome electrostatic forces holding the copy sheet to the imaging drum, the sponge roller is advantageous as it can firmly contact the copy sheet and imaging drum. i

There are many other ways in which stripping from the drum 10 can be achieved. For example, the drum 10 may have. a recessed surface portion and may be arranged so that when the paper is fed to the drum .its

' leading edge slightlyoverlies this recess and is thereby accessible to lifting or. gripping fingers provided for separating, or at least initiating the separation of, the paper from the drum, the fingers being moved in a manner appropriate to'the rotational movement and speed of the drum. If desired, a thin rod or wire may extend in the recess and may be raised when it reaches the stripping zone 17, to raise the leading edge of the paper from the drum to facilitate its being gripped by the stripping means. Another device, which does not require the drum angular position to be synchronised with the paper feed, provides a wire or rod, extending against or close to the drum surface and parallel to its axis supported for example between arms at the ends of the drum, which is interposed between the drum surface and the leading edge of the paper as this is fed to the drum. The wire or rod then travels round with the drum and paper until, at the stripping zone (17 in FIG. 1) it is moved away from the drum to engage the leading edge of the paper with fingers or with a suction drum, which then takes over the stripping action, after which the wire or rod returns to its starting position.

In a case where the leading edge. of the copy paper is accessible, or made accessible by any of the means described above, the suction drum 51 of FIG. 1 may be replaced by a stripping'separator drum provided with mechanical stripping fingers which engage the leading edge of the paper and then separate it from the drum 10 by rotation of the separator drum. Again, the suction drum may be used in combination with these de-. vices which assist in separating the leading edge of the paper.

In a different way of controlling the progress of the copy paper, a continuous band conveyor may be provided with means for engaging the paper, the conveyor path leading from a point, at which the paper can be manually or otherwise fitted, to the transfer zone where the paper contacts the drum l and has the image transferred to it, and thence to and through the fuser unit and to a point where the paper can be removed before the conveyor returns to its first-described position.

Alternatively a non-continuous conveyor system may be employed in which a conveyor band with means for attaching the copy paper is movable back and forth along a path which passes in sequence all the stations above mentioned.

After the paper or other sheet material has been stripped from the drum 10 at the zone 17, the drum requires cleaning before the cycle is repeated. A cleaning unit provided for this purpose comprises a roll 60 of I drum surface. The web 61 is taken between rollers 62 and 63, one of which is driven so as to unwind the roll 60 by rotating it in the opposite sense to that in which the rotating drum l0 urges it; A further spool is driven through a slipping clutch to wind up the web 61, as it leaves the rollers 62 and 63, into a second roll 64. FIG.

1 shows in broken lines the changed configuration which obtains when a web 61 has been almost completely transferred from the roll 60 to the roll 64. Preferably, the whole cleaning unit assembly is mounted on the underside of a panel, constituting part of the top surface 25, which can be hinged up to swing the cleaning unit assembly clear out of the body of the apparatus. This gives particularly easy access when it is required to replace a used roll of cleaning material. Instead of the rollers 62 and 63, a single driven roller may be provided in contact with the roll 60, thereby to control the linear speed at which it is unrolled by the tension which is applied by the roll 64 and which overcomes the torque exerted by friction of the drum 10 or,

again, the roll 64 may be driven not through a slipping clutch but at constant peripheral speed by a driven roller in surface contact with it, thereby to unwind the roll 60 at constant linear speed.

The resilience of the web on the roller 60 ensures broad contact with the drum 10. Thus the effect of a resilient roller urging a single thickness of web against the drum is achieved without having to provide the resilient roller.

One very suitable material for use as a cleaning web 61 for cleaning the drum surface is the unwoven openmeshed type of cloth available from Johnson & Johnson Ltd. under the trade mark .I-Cloth. Another type of cleaning unit for which this open-meshed material is particularly suitable is shown in FIG. 5, in which the web 61 drawn from roll 60 and taken up on roll 64 is pressed into frictional engagement with the drum 10 by means of rubber rollers 81 and 82 (either tensioned or of sponge rubber and therefore not necessarily tensioned) which are spaced apart and between which is disposed a suction duct 83 by means of which toner powder cleaned from the drum surface by the web 61 is to a large extent removed from the web and its vicinity to be caught in a stationary filter (not shown) prowith detergent liquids (with or without the addition of water) or with soap solution or with honey (alone or diluted with water).

, It will be understood that many of the component units in the apparatus shown in FIG. 1 may be replaced by other units serving the same or equivalent function. For example, the above-described provision of the paper or other material in the form of a continuous roll may be selected as probably the simplest means by which an automatic feed of copy paper as required can be achieved, but other paper feed arrangements may be embodied additionally or alternatively. For example,

. particularly in a low-priced machine designed to allow copying at minimum cost, it may be acceptable to provide a tray on which an operator can place a single sheet ofpaper on which a copy is to be made, the machine then taking this sheet and feeding it at the appropriate moment by simple mechanism which need incorporate no refinements to ensure that only a single sheet is fed at one time. Thus it is possible to provide a paper tray which holds a stack of paper sheets and is provided, in known manner, with means for picking off only a single sheet at once and feeding it to the image. transfer zone. Such a tray could be used, for example, to supply copy paper of one standard size, paper from the roll 44 being used when larger originals were being copied.

The drum is described above as being provided with a photoconductive surface layer. This may, of course, be achieved in various ways. The surface of the drum may itself be sufficiently smoothly finished that it has the sensitive surface layer deposited on it directly, for example. by vacuum evaporation, or the drum may be simply a support for a sensitive surfaced plate or plates secured thereon by one of a variety of means.

Although the apparatus shown in FIG. 1 is designed to operate with its drum 10 rotating continuously at uniform speed, and to go through a complete copying cycle at each revolution, this is only one of several possible arrangements. For example, it may be arranged that the drum rotates once to be charged, exposed and developed all over its operative surface, and then makes a second revolution, in the same or opposite direction, duringwhich transfer of the image to a copy paper and subsequent cleaning of the drum are affected. The first revolution may be at slower speed, to give longer exposure or, perhaps, finer development; or in a particular case it may be desirable that the second revolution .be slower. The reversal of direction may, in a particular design, facilitate the appropriate feeding of the copy paper to the drum for image transfer thereto. in any of the arrangements, the copy paper may be fed to the drum adjacent the developer unit after (if desired) having been fed along below the developer unit. If developing and copy-paper feeding are not taking place simultaneously, however, the copy paper may be fed through between the developer uni-t and the drum (andin contact with the latter) at a time when the developer unit is inactive and the developer it contains is out of contact with the drum.

It will be understood that, particularly when the copy paper is drawn from a continuous roll 44 and the continuous l-revolution cycle operation shown in FIG. 1 is employed, there is effectively no limit to the length'of original document which can be copied. It is to be noted that, with the illustrated designs of the various 12 units, there is virtually no practical limit to the width to which the apparatus may be built; and it follows that a machine according to the inventionmay be quite small (i.e. a desk-top machine and yet be capable of copying surprisingly large original documents.

If desired, the drive to the rollers 26 and 27 of the saddle 24 may be reversible, under the control of sensing devices which sense when the trailing edge of an original, as it is fed in either direction, clears the window 20; by this means an original may be caused to feed back and forth over-the window, one copy being made during each forward pass of the original until the required number of copies has been made.

I claim: i

1. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied'at said exposure station, a fixing unit for fixing developer material onto a copy sheet by the application of heat,said light source being associated with said fixing'unit to provide heat thereto, a movable bottom wall to said fixing unit, said movable wall being movable between a first position wherein said unit is closed and a second position wherein said unitis open to receive a copy sheet.

2. Apparatus as claimed in claim 1 and further comprising thermoinsulating walls defining said fixing unit,

' said light source being located within said fixing unit,

and a. transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station.

3. Apparatus as claimed in claim 1 and further comprising at least one heat source in said fixing unit.

4. Electrostatographic copying apparatus comprising a substantially horizontal exposure window over which an original to be copied may be moved to be illuminated, a flexible transparent sheet of plastics material extending over said window, a roll and a transverse rib on said sheet, said sheet being windable onto and off said roll to be drawn over said window, whereby an original to be copied when placed upon said sheet adjacent said rib is moved over said window.

5. Apparatus as claimed in claim 4 and further comprising a drive roller in contact with the surface of said sheet on said roll.

6. Apparatus as claimed in claim 4 and further comprising a flap and a housing for said apparatus, hinge means connecting said flap to said housing, said flap having a free end remote from said hinge means and being rotatable to and restrainable in an operative position wherein it is substantially coplanar with said window, said roll being positioned at said free end of said flap.

7'. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposureof originals to be copied at said exposure station, and a fixing unit near said exposure station for fixing developer material onto a copy sheet by the application of heat, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit to provide heat thereto, a transparent section on at least one of said walls said section being disposed relative to said exposure station so that light may pass there through toward said, and an opaque flap movable to and from a position in which it covers said transparent section.

8. Apparatus as claimed in claim 7 and further comprising at least one heat source in said fixing 'unit.

9. Apparatus as claimed in claim 7 and further comprising a reflector adjacent said exposure station to concentrate light thereon.

10. Apparatus as claimed in claim 7 and further comprising a movable shield for said light source, said shield being movable to a position to reflect light through said transparent section when said flap is not in said position in which it covers said transparent section.

11. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a fixing unit near said exposure station for fixing developer material onto a copy sheet by the application of heat, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit to provide heat thereto, a transparent section on at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station, a rotatable shield for said light source, said shield being rotatable between a first position in which it directs radiation from said light source through said transparent section, and a second position in which it directs radiation from said light source towards a copy sheet in said fixing unit.

12. Apparatus as claimed in claim 11 and further comprising at least one heat source in said'fixing unit.

13. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit near, said exposure station for fixing said developer material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit, a transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station and an opaque flap movable to and from a position in which it covers said transparent section.

14. Apparatus as claimed in claim 13 and further comprising a movable shield forsaid light source, said shield being movable to a position to reflect light through said transparent section when said flap is not in said position in which it covers said transparent section.

' 15. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge'said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit near said exposure station for fixing developer said material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit, a transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station, and a rotatable shield for said light source, said shield being rotatable between a first position in which it directs radiation from said light source through said transparent section and a second position in which it directs radiation from said light source towards a copy sheet in said fixing unit.

16. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit for fixing said developer material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit and a movable bottom wall to said fixing unit, said movable wall being movable between a first position wherein said unit is closed and 'a second position wherein said unit is open to receive a copy sheet. 

1. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a fixing unit for fixing developer material onto a copy sheet by the application of heat, said light source being associated with said fixing unit to provide heat thereto, a movable bottom wall to said fixing unit, said movable wall being movable between a first position wherein said unit is closed and a second position wherein said unit is open to receive a copy sheet.
 2. Apparatus as claimed in claim 1 and further comprising thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit, and a transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station.
 3. Apparatus as claimed in claim 1 and further comprising at least one heat source in said fixing unit.
 4. Electrostatographic copying apparatus comprising a substantially horizontal exposure window over which an original to be copied may be moved to be illuminated, a flexible transparent sheet of plastics material extending over said window, a roll and a transverse rib on said sheet, said sheet being windable onto and off said roll to be drawn over said window, whereby an original to be copied when placed upon said sheet adjacent said rib is moved over said window.
 5. Apparatus as claimed in claim 4 and further comprising a drive roller in contact with the surface of said sheet on said roll.
 6. Apparatus as claimed in claim 4 and further comprising a flap and a housing for said apparatus, hinge means connecting said flap to said housing, said flap having a free end remote from said hinge means and being rotatable to and restrainable in an operative position wherein it is substantially coplanar with said window, said roll being positioned at said free end of said flap.
 7. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, and a fixing unit near said exposure station for fixing developer material onto a copy sheet by the application of heat, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit to provide heat thereto, a transparent section on at least one of said walls said section being disposed relative to said exposure station so that light may pass therethrough toward said, and an opaque flap movable to and from a position in which it covers said transparent section.
 8. Apparatus as claimed in claim 7 and further comprising at least one heat source in said fixing unit.
 9. Apparatus as claimed in claim 7 and further comprising a reflector adjacent said exposure station to concentrate light thereon.
 10. Apparatus as claimed in claim 7 and further comprising a movable shield for said light source, said shield being movable to a position to reflect light through said transparent section when said flap is not in said position in which it covers said transparent section.
 11. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a fixing unit near said exposure station for fixing developer material onto a copy sheet by the application of heat, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit to provide heat thereto, a transparent section on at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station, a rotatable shield for said light source, said shield being rotatable between a first position in which it directs radiation frOm said light source through said transparent section, and a second position in which it directs radiation from said light source towards a copy sheet in said fixing unit.
 12. Apparatus as claimed in claim 11 and further comprising at least one heat source in said fixing unit.
 13. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit near said exposure station for fixing said developer material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit, a transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station and an opaque flap movable to and from a position in which it covers said transparent section.
 14. Apparatus as claimed in claim 13 and further comprising a movable shield for said light source, said shield being movable to a position to reflect light through said transparent section when said flap is not in said position in which it covers said transparent section.
 15. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit near said exposure station for fixing developer said material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit, thermoinsulating walls defining said fixing unit, said light source being located within said fixing unit, a transparent section in at least one of said walls, said section being disposed relative to said exposure station so that light may pass therethrough toward said exposure station, and a rotatable shield for said light source, said shield being rotatable between a first position in which it directs radiation from said light source through said transparent section and a second position in which it directs radiation from said light source towards a copy sheet in said fixing unit.
 16. Electrostatographic copying apparatus comprising an exposure station, a light source for the exposure of originals to be copied at said exposure station, a drum, a surface layer of photosensitive material on said drum, means to charge said layer, means to direct light from said exposure station to said drum to selectively imagewise discharge said layer, developer means to develop residual charge images on said drum with developer material, a transfer station adjacent said drum, means to forward copy sheets to said transfer station to receive thereat developer material from said drum, a fixing unit for fixing said developer material onto said copy sheets by the application of heat, said light source being associated with said fixing unit such that heat from said light source is used in said fixing unit and a movable bottom wall to said fixing unit, said movable wall being movable between a first position wherein said unit is closed and a second position wherein said unit is open to receive a copy sheet. 